Comprehensive analysis and implications of Veronica persica germination and growth traits in their invasion ecology

Invasive alien species implications in ecological threats are attributed to their unique characteristics that are linked to their invasion. Veronica persica (Plantaginaceae family) is an alien weed species in Egypt. Regardless of its widespread globally in various regions, the growth traits and behavior of V. persica remain poorly understood. The comprehensive analysis, reveals the optimal germination (Gmax) was detected at 10/20 °C, 15/20 °C, and 20/25 °C at the moderate temperature regimes. The rapid germination rate (G rate) peaked at 10/20 °C regime, with a rate of 0.376 per day. Furthermore, under stress conditions, V. persica has 50% germination inhibition (G50) and 50% of growth inhibition occurred at − 0.91 MPa and 0.75 MPa of osmotic pressure and 3225.81 ppm and 2677.1 ppm of salt stress (NaCl) respectively. The germination ranged from 6 to 9 pH, with the highest germination percentage occurring at a pH of 7 & 8, reaching 88.75% compared to the control group. There is a strong interaction effect between habitats and plant stages, the plant stages and habitats have significant effects (p ≤ 0.00) on V. persica growth. There was high and moderate plasticity in the response of morphological and growth features between stages. During the seedling-juvenile interval and the juvenile-flowering stages, respectively, there was a noticeable increase in both Relative Growth Rate and Net Assimilation Rate. Demographic surveys identified approximately 24 species across 11 families associated with V. persica in invaded areas. The Sorenson indices of qualitative index exhibited high similarity values in the invaded sites by (82.35%) compared to (72.72%) in non-invaded sites. However, interactions with native communities were reflected in lower richness, diversity, and evenness, displaying slightly higher Simpson index 1 (λ) values compared to invaded and non-invaded sites (0.043 and 0.0290) vs. (0.0207 and 0.268), in rangelands and F. carica orchards respectively. These results emphasize the substantially higher adaptability of V. persica to variable environmental conditions and abilities to invade a new community. This knowledge about invasive V. persica weeds germination and growth is itemized as the consistent predictive base for future invasion and informs strategic management priorities.

were particularly prone to alien invasions and very efficient donors of alien plants to other patches.Salt marshes were in general very resistant to invasion but potentially acted as secondary reservoirs for some backdune alien species 10 .Invasive species display several features including fast growth rates, high reproductive rates, greater dispersal capacity, and high adaptability to a broad range of environmental conditions linked to their invasion success, [11][12][13] .Therefore, it is hard to control invasive and alien weeds once they are established 14 .The increase in alien plant invasions is primarily a result of the increased application of chemical fertilizers and herbicides 15 .The impacts of invasive alien species on ecosystem structures and functions are paramount for implementing appropriate management and restoration strategies 16 .Identifying the long-term trajectories of phenotypic changes in invasive species provides important clues for their appropriate management 17 .Knowledge of biological invasions is important for controlling the current distribution, understanding the causes, and mitigating the associated risks and consequences 18 .
Understanding responsible traits for promoting plant invasiveness could be important to aid in the development of adequate management strategies 19 .These traits vary from one stage to another in the life cycle of invasive species 20,21 .Functional traits may contribute to their success by enhancing niche differences or providing invasive species with competitive advantages 22 .Differences in plant morphological and physiological traits between invasive and native species are often associated with invasiveness 23 .The germination stage is a key process during the expansion of species 24 .Invasive species typically exhibit higher specific leaf area and relative growth rate 25 , as well as longer flowering and fruiting periods 26 .Relative growth rate serves as a significant determinant of the competitive ability of exotic plant species following disturbance 27 .Relative growth rate is a physiological measure that can be used as a predictor for invasiveness in disturbed habitats 28 .Trait plasticity can explain why some invasive species exhibit a better ability to establish themselves in a wide range of environments 29,30 .Higher plasticity refers to the substantial adaptability to variable environmental conditions 31 .
Veronica L. is the largest genus within the Plantaginaceae (Veronicaceae), boasting around 23,000 species 32,33 .Veronica persica has been identified as a weed in 27 crops across 45 countries 34 .It demonstrates robust germination in both light and dark conditions, thriving particularly well at 35 °C at a 2 cm depth 35 .The reproductive effort was fairly similar for both annuals and perennials of Veronica species, which varied in their habitats and aggressiveness as weeds 36 .The native Veronica polita subsp.lilacina placed closer to the alien V. persica suffered a greater decrease in fruiting success 37 .V. persica has special competitive effectiveness due to its polyploidy which can produce greater variations within its ecotypes 38 .This species is an alternative host for various crop pests and pathogens [39][40][41] .The average seed number is 50-100 seeds per plant 42 , while, it showed a mean annual decline of 18% and a half-life of 3.5 years 43 .The success of this weed is ensured by the large number of seeds and by the fact that it survives over the winter season, and is immune to frost 44 .V. persica has the ability to root at the nodes and can reroot following surface cultivation making it difficult to control mechanically 45,46 .V. persica has a high capability to produce flowering structures and a significant rate of seed production 47 .The alien farmland weeds of the genus Veronica exhibit adaptability to varying illumination conditions, and their asexual reproduction traits may contribute to their successful invasion 48 .Invasion of V. cymbalaria into areas where V. persica prevails is unlikely, although swift displacement of V. cymbalaria by V. persica in areas where V. cymbalaria is already established is also unlikely during the interference investigation 49 .
Ecological information about invasive alien species is very important for prevention methods and control efforts.In Egypt, there is inadequate knowledge about the invasive V. persica species seed behavior in the invaded areas.The study hypothesized that the ecological dynamics of V. persica will affect their behavior invasion in the new areas based on their pattern of germination and plasticity of the growth.Moreover, these results provide the base for predicting their future invasions and beyond their ecological zones.Therefore, the study aimed to test the germination and growth traits of V. persica under various environmental factors.Quantifying their ecological indices in their auto ecosystem communities and across different habitats to insights into the interactions between the invasive species and the native.
The average of V. persica germination percentage over five consequences temperatures grouped ranges was 42.33% (low-temperature regime) 78.34% (moderate-temperature regime), 34.0% (high-temperature regime), 25.25% (large high and low-temperature regime) and 6.833% (extremely high-temperature regime) respectively.The highest germination abilities recorded in V. persica that setting up seed germination in most temperatures and resilient adaptability in wide temperatures regimes included low, high temperature and extremely hightemperature regimes (Fig. 1).

Life stages and growth analysis under natural habitats
The emergence of V. persica seeds takes place from December to May, while massive germination occurs in February and March during each year.Seedling, juvenile, flowering, seeding, and dispersion stages were distinguished with a short time of seedling and juvenile.However, the flowering stages are prolonged from March until July and occur two months after emergence.On the other side, seeding and dispersion stages are extended in the summer season (Fig. 3).
The growth traits of V. persica species were investigated during the growth stages in rangelands and F. carica orchards.The analysis revealed a significant (p ≤ 0.00) increase in total dry biomass, root weights, shoot weights, leaf mass, leaf area, and seed traits from the initial stages, reaching their optimum at the seed stage.While, the habitats have significant effects (p ≤ 0.00) on total dry biomass, root weights, shoot weights, leaves mass, and seeds respectively.The interaction effects of habitats and plant stages were significantly detected in total dry biomass, root weights, shoot weights, leaves mass, and seeds (Table 2).Regarding the phytomass accumulation at different stages for each trait, All growth traits exhibited high plasticity in their response among stages in both while these traits are lower in F. carica orchards than rangelands of total dry biomass, root dry weight, stem dry weight, leaves dry weight, lengths, leave area and leaves number.While, all morphological traits exhibited moderate plasticity in their response among stages in both rangelands and F. carica of Shoot to root ratio, leaf area ratio, leaf mass fraction, root mass fraction, stem mass fraction, specific leaf area, and specific stem length (Table 2).
The relative growth rate (RGR) of V. persica was important as a key for growth measurement and competition with other plant species.The maximum RGR observed in the seedling-juvenile interval and develops slowly during the juvenile-flowering interval, then develops with a small rate at the remaining seeds and dispersing intervals, (F = 251.76,p ≤ 0.00) life stages.The net assimilation rate (NAR) is associated with photosynthetic and respiration rates.In general, there was a significant increase (F = 174, p ≤ 0.00) observed across the stages until www.nature.com/scientificreports/ the final stage.The net assimilation rate (NAR) was greatest in the juvenile and flowering stages but was lower in the seed and dispersing stages (Fig. 4).

Demographic analysis of the vegetation community associated with V. persica
The accompanying plants to V. persica species were 24  respectively.While the quantitative index showed high values in the invaded sites (67.4%) compared to the noninvaded sites (49.3%) respectively (Fig. 5).
The richness index of R1 and R2 was higher in invaded sites compared to non-invaded sites of rangelands, and F. carica orchards.The evenness of Hill's index (E4) and Modified Hill's ratio (E5) were higher in non-invaded areas compared to invaded areas (Fig. 6).The diversity indices of the Simpson index 1 (λ) were observed slightly higher in non-invaded sites by 0.043 and 0.0290, compared to invaded sites with values of 0.0207 and 0.268 respectively in rangelands and F. carica (Fig. 7).

Relative growth rate (RGR)
Net assimilation rate

Discussion
The limited information about invasive V. persica species potentials in invaded areas led to the implementation of this study to investigate its germination, and growth traits under environmental conditions as best predictors for future invasion and behavior in new habitats.The invasive species V. persica (Plantaginaceae) is native to Europe and parts of Asia but has spread globally as an aggressive weed and high invasion level 48 .Plant invasiveness has been correlated with seed germination traits 50 .The growth form, vigor, and rapid seed germination of V. persica are significant factors in their spreading and establishment 51 .The germination ability under a wide range of environmental conditions indicates an increased potential for invasion into non-infested areas 52 .On the basis of findings, V. persica seed germination preference was in moderate temperature regimes followed by low, and high-temperature regimes, consequently, their germination is limited in both widely fluctuating and extreme temperature regimes.The emergence of V. persica takes place from December to May, while the massive germination occurs in February and March annually.Generally, in various temperature regimes, the species exhibits high values and abilities to achieve maximum germination (G max ) have a shorter time for 50% germination (T 50 ), and a rapid germination slope (Grate) 53,54 .Seed of V. persica emerged from February to November with peaks in May and September 55 .V. persica seeds exhibited full germination when exposed to light, whereas there was only 67% germination in the dark 56 and there was 67% germination at alternating temperatures under a 'safe' green light 57 .The germination timing of V. persica was less specific and occurred at several periods during the autumn, spring and summer 58 .Temperature is an important factor affecting the successful invasion and the establishment of populations that greatly affects seed germination and plant growth 59 .The invasion success is attributed to a high germination rate 60,61 .Under respective levels of environmental stress including osmotic pressure, salt stress and varied pH levels, V. persica exhibited supreme tolerance to osmotic potentials (drought), with half germination (G 50 ) at − 0.915 MPa with occasionally limited ability to germinate in high osmotic pressures, this osmotic potential presented 50% of growth at − 0.75 MPa.Similarly, the high salt stress concentration (5000 ppm) was not favorable for V. persica to germinate.It presented G 50 % at 3225.81 ppm and half growth at 2677.1 ppm.On the other side, the majority of germination was found at moderate pH levels, whereas, decreasing and increasing pH levels negatively affected V. persica germination.Based on these results, V. persica demonstrated good adaptability to germinate and establish seedlings in varied environmental conditions, including droughts, salt stress, and diverse pH levels.These results harmonized with the findings that V. persica Poir germinated well in both light and dark conditions 35 .In the field, V. persica germination was high (≥ 10%), affected by the date and depth of cultivation 62 .The presence of invasive weeds in diverse geographical regions has a considerable impact on both biodiversity and the ecological system 63 .The growth pattern of V. persica was recorded based on the high relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and specific leaf area (SLA) which reflect high dry mass accumulation coefficient during the developmental growth.These traits give V. persica a better competitive ability as compared with the native species.Seedling relative growth rate analysis is a powerful tool for understanding life-history traits 28 .The growth form, vigor and extent of adventitious root production and rapid seed germination of V. persica were considered to be significant factors in their spreading and establishment 64 .Under a shaded environment, V. persica decreased its leaf mass per unit area (LMA) to minimize the carbon costs associated with photosynthesis and allocate more carbon for individual growth 65 .V. persica contributes to population recruitment through the vigorous growth of its adventitious roots 64 .Growth of V. persica is strongly suppressed in shade 66 .The high RGR of invasive species is advantageous initially when seedlings experience little or no competition and/or herbivory 67 .High RGR associated with opportunistic resource acquisition and increased root allocation to survive summer drought may be critical for the success of plant invaders in regions with Mediterranean climates 68 .Invasiveness is strongly related to leaf traits and fast relative growth rate that is associated with rapid carbon capture 69 .The rates of relative growth, shoots/roots ratio, leaf area ratio, and leaf mass fraction are influenced by various stages and habitats 70 .Meanwhile, V. persica has a high plasticity index among growth stages that reflects strong phenology traits and adaptabilities to harsh environmental conditions 71 .

Rangelands
F. carica www.nature.com/scientificreports/Alien species have strong adaptability to new habitats 72 .There is a strong correlation between vegetative growth and reproductive ability that contributes a lot to the successful invasion of V. persica 73 .The ecological indices in invaded and non-invaded localities revealed, A little differentiation of Simpson index 1 (λ) in rangelands and F. carica by 0.025 and 0.026 (non-invaded) as compared with 0.022 and 0.219 (invaded) respectively.However, the coefficient of similarity is higher within the invaded and the non-invaded crop areas.Therefore, invasion by V. persica can reduce species diversity with fewer values of diversity, richness and evenness indices based on the invasion force, these detrimental impacts are caused by the displacement of native species.These results align with Fischer 74 who reported that V. persica is allotetraploid adapted to become a highly successful weed with a large ecological range.While their congeneric alien species (V.hederifolia) has already obviously declined the biodiversity in the distribution area in China 75 .Alien Veronica species (V.persica) can capture resources successfully by increasing root biomass under shade environments 76 .Invasive species own a wider range of conditions with faster germination and higher germination rates 77,78 .While, rising temperatures due to climate change are expected to interplay with biological invasions, and may enhance the spread and growth of some alien species upon arrival in new areas 8 .A changing climate may alter the likelihood of introduction or establishment, as well as modify the geographic range, environmental impacts, economic costs or management of alien species 79 .Finally, the above result confirms the significant potential of V. persica to germinate under environmental stress, achieving maximum germination (G max ), shorter time for 50% germination (T 50 ), and a rapid germination slope (G rate ) in various temperature regimes.The high accumulation coefficient and plasticity of biological traits may contribute to the extended invasion of the species.Generally, there is an association between V. persica germination parameters and growth traits that could act as enabling forces for invasion, spread, and colonization in new areas.Therefore, it is crucial to take all possible actions to prevent their invasion into other geographical zones.

Plant materials
Plant specimens of naturally occurring Veronica persica Poir.were collected from the northwestern coast of Egypt from December to June.Voucher samples (CAIH-16-4-2022-V) were characterized by Dr. Emad Abdel-Kader, a plant specialist at the Desert Research Center, according to Tâckholm 80 and Boulos 81 .The seeds were harvested in May and cleaned before drying in paper bags at 15 °C and 15% relative humidity and then stored in sealed vials during the germination experiment at the same conditions.The climate in this region in the winter season is rainfall, and hot dry in summer.The soil analysis revealed the following composition of 86.00% sand, 8.65% silt, and 6.35% clay respectively.The soil has ranged from 8.12 to 8.3 (pH), and 2.837 and 1.339 ds/m (electrical conductivity) respectively.Additionally, the soil contained sodium (27.721-1559 meq/l), potassium (1.145-1.098meq/l), calcium (6.39-5.99meq/l), magnesium (5.149-4.577meq/l), carbonate (0.432-0.361 meq/l), bicarbonate (2.205-1.66meq/l), and chloride (6.805-6.17meq/l) respectively, according to established soil analysis methods FAO-UNESCO 82 .

Germination experimental process
The investigation of V. persica seed germination involved subjecting to 36 alternating temperature regimes ranging from 5 to 40 °C, with increments of 5 °C.These combinations can be categorized according to Pitcairn et al. 83  Twenty-five seeds were sterilized using 0.3% sodium hypochlorite and then positioned in 9 cm Petri dishes containing two layers of filter paper moistened with distilled water.Each treatment was replicated four times and then placed in the incubator to be subject to the tested alternating temperatures ranging from 5 to 40 °C under a 12/12-h light/dark.This design followed a completely randomized pattern and was repeated at least two times to minimize errors.The number of germinated seeds was recorded daily at the same time for 30 days.

Impact of environmental stress on V. persica seed germination and growth.
To explore the influence of osmotic pressure on the germination and growth of V. persica, Polyethylene glycol (PEG) 8000 from Sigma-Aldrich, USA, was dissolved in deionized water to produce osmotic potentials of 0.0, − 0.20, − 0.40, − 0.60, − 0.80, and − 1.00 MPa.These potentials were achieved by incorporating 0.00, 99.40, 157.10,  222.20, 314.20, and 384.80 g of PEG 8000, respectively.This method follows the protocol outlined by Michel 84 and Michel and Radcliffe 85 .To assess the impact of salt stress, NaCl solutions with concentrations of 0.0, 500.0,1000.0,2000.0,3000.0,4000.0, and 5000.0 ppm were chosen to reflect the salinity levels found in Egyptian soil 86 .Finally, to assess the impact of varied pH levels ranging from 1.0 to 12.0, the pH solution was prepared following the method outlined by Burke et al. 87 .Twenty-five sterilized seeds of V. persica were positioned on filter paper placed on Petri dishes, moistened with ten milliliters of the respective test solution, and then incubated at 20/10 °C (the optimum temperature regime) under a 12-h light/12-h dark cycle.Daily counts of germinated seeds were conducted for 30 days, and the results were expressed as percentages of germination.To examine their impact on seedling growth, one seedling, seven days of age, was immersed in each concentration within a tissue culture tube for a duration of two weeks, with five replications.Subsequently, the total fresh biomass weight was recorded 86  The V. persica samples were gathered during regular visits to the invaded area and sorted at different stages to examine their growth and development.The weights, lengths and leaf area per plant were carried out on 20 tagged plants of seedling, juvenile, flowering, seeds and dispersal stages of growth and phenology according to West and Wein 88 , whereas, leaf area ratio (LAR), root/shoot ratio (R/S ratio), leaf mass fraction (LMF), root mass fraction (RMF), stem mass fraction (SMF), specific leaf area (SLA), and specific stem length (SSL) were determined.Relative growth rate (RGR) and Net assimilation rate (NAR) were measured Cornelissen et al. 89 , and Gregory 90 respectively.The phenotypic plasticity index is according to the following formula: IPF = (value of maximum mean -value of minimum mean)/(value of maximum mean) for each trait 91 .

Comparison of V. persica communities within invaded and non-invaded sites
A field survey to quantify the occurrence of V. persica in rangelands and Ficus carica (fig) orchards on the north coast of Egypt from February to August 2021 and 2022.A total number of sites 40 included were surveyed for occurrence in rangelands and F. carica according to Thomas 92 and Thomas et al. 93 .The number of species weed density and frequency determined.The V. persica communities under rangelands and F. carica systems were compared using 'Sorenson's Indices of Similarity' 94 that allows for comparison of stability between invaded and non-invaded situations over via Qualitative index or indices of similarity obtained from = [2C/(A + B)] × 100 where C = Number of species in common, A = Total number of species in the area A and B = total number of species in the area B.Richness, diversity index and evenness were provided according to Margalef 95 , Margalef 96 , Pielous 97 , Magrurran 98 .

Data analysis and statistics
The germination was represented as cumulative percentages and subjected to nonlinear regression models employing a three-parameter sigmoid curve using Sigma Plot® 12.5 software, under various temperature conditions according to Evans and other 99 , and Lu et al. 100 .The employed model is G % = G max /1 + e [(− x − T 50) ] G rate .
Where G represents the cumulative percentage germination at time x, G max is the maximum germination (%), T 50 is the time (d) required for 50% of maximum germination and G rate indicates the slope of the curve in T 50 .
The germination percentage of salt stress, osmotic potential, and different pH levels data were subject to the same equation to determine 50% inhibition of the maximum germination 83 .The growth records are subject to secondorder polynomial regression equations; F = (Y0 + a*X + b*X 2 + c*X 3 ) derived from the relationship between; F is the phenotypic trait value, Y0 are fixed effects of the overall intercept, (a), (b), and (c) are fixed components of the model, X is the weights variable 70 .All data from the four replications were analyzed using analysis of variance (ANOVA) in IBM SPSS Statistics 21.Where, Tukey test was employed to compare differences within each species, and statistical significance was considered at p ≤ 0.05.

Guidelines of material collections and studies
All the steps of experimentation on V. persica weeds, including the collection of plant material, are in compliance with relevant Institutional, National, and International guidelines.The studies were conducted in accordance with local legislation and with permissions from our institutes and complied with the IUCN Policy Statement.

Figure 1 .
Figure 1.The average of germination in five consequences temperature ranges.

Figure 2 .
Figure 2. Effect of environmental stress in V. persica seeds germination.

Figure 3 .
Figure 3. V. persica germination and growth life stages during the year.

Figure 4 .Figure 5 .Figure 6 .
Figure 4. Relative growth rate and Net assimilation rate of invasive species during growth stages.

Figure 7 .
Figure 7. Simpson indices of diversity in invaded and non-invaded sites.

Table 2 .
Plasticity index of V. persica and multivariate analysis of growth stages in different habitats.*D.Wt = dry weight.